Assemblies and methods for reducing particulate matter, hydrocarbons, and gaseous oxides from internal combustion engine exhaust

ABSTRACT

Exhaust generated from an internal combustion engine includes particulates and gas-phase volatile hydrocarbon condensables. The exhaust is cooled in an exhaust gas cooler from a first temperature to a second temperature such that a first portion of the gas-phase volatile hydrocarbon condensables in the exhaust condense to the liquid phase and a second portion of the gas-phase volatile hydrocarbon condensables in the exhaust condense on black carbon particles to form semivolatile brown carbon particulates. Some or all of the liquid-phase volatile hydrocarbon condensables and the semivolatile brown carbon particulates are trapped in a gasoline particulate filter or a catalyzed gasoline particulate filter located downstream of the exhaust gas cooler.

RELATED APPLICATIONS

The present application is a divisional of and claims the priority ofU.S. Application Ser. No. 15/892,599, entitled “Assemblies and Methodsfor Reducing Particulate Matter, Hydrocarbons, and Gaseous Oxides fromInternal Combustion Engine Exhaust,” filed on Feb. 9, 2018, which claimspriority to, and benefit of Provisional Application No. 62/457,846,filed on Feb. 11, 2017. The foregoing applications are herebyincorporated by reference.

TECHNICAL FIELD

The present application relates generally to emissions control systemsfor internal-combustion engines.

BACKGROUND

Vehicle emissions are highly regulated to minimize the output ofenvironmentally-harmful exhaust emissions. The major regulatedpollutants include carbon monoxide (CO), nitrogen oxide compounds(NO_(x)), and unburned hydrocarbons (C_(x)H_(y)). If the vehicle exhaustis left untreated, the levels of pollutants would far exceed theemissions standards set by, for example, the U.S. EnvironmentalProtection Agency, the states, or another country.

To meet these standards, vehicles include exhaust treatment systems thatinclude catalytic converters, such as three-way catalytic (TWC)converters, to convert gaseous CO, NO_(x), and C_(x)H_(y) into lessharmful compounds through oxidation and reduction reactions. An exampleof such an exhaust treatment system is illustrated in FIG. 1, which is ablock diagram of an underbody of a vehicle 10. The vehicle 10 includesengine 100, first catalytic converter 110, second catalytic converter120, and muffler 130, which are in fluid communication with one anotherthrough pipe or conduit 140. In operation, the engine 100 generatesexhaust, which travels through conduit 140 to first catalytic converter110, second catalytic converter 120, muffler 130, and then into theenvironment through tail pipe 150.

Recently, emissions regulators have become increasingly concerned aboutparticulate emissions and setting limits on their levels in engineexhausts both in terms of their total mass (PM) and number (PN). Theseparticulates are generated in internal combustion engines in three basicforms: (1) condensables (also referred to as PM2.5 when their size isless than 2.5 microns), (2) pure solids, generally referred to as “blackcarbon,” and (3) carbon particles saturated with volatile hydrocarboncondensables, generally referred to as semivolatile particles or “browncarbon.” At the high temperatures typical inside a standard exhausttreatment system (e.g., about 650° F. to about 1250° F.), such as thatillustrated in FIG. 1, some particulates form before the exhaust gasesreach the tailpipe, while some of the volatile hydrocarbon condensablesremain in their gaseous phase. After exiting the tailpipe, volatilehydrocarbon condensables cool and return to the liquid phase, appearingas an aerosol. The final state of the condensables depends on thetemperature, degree of dilution, other particulates in the atmosphere,etc.

Gasoline particulate filters (GPFs) and catalyzed gasoline particulatefilters (cGPFs), coupled in some form to a catalytic converter, havebeen proposed for removing particulates from hot exhaust gases beforethey exit the tailpipe. However, GPFs and cGPFs cannot remove volatilehydrocarbon condensables in their gaseous form. In addition to exitingthe exhaust system as a liquid (e.g., as an aerosol), gaseous volatilehydrocarbon condensables can form additional particulates downstream ofthe GPF/cGPF, for example in the muffler or as they exit the tail pipe.

It would be desirable to overcome one or more of the foregoing problems.

SUMMARY

Example embodiments described herein have innovative features, no singleone of which is indispensable or solely responsible for their desirableattributes. The following description and drawings set forth certainillustrative implementations of the disclosure in detail, which areindicative of several exemplary ways in which the various principles ofthe disclosure may be carried out. The illustrative examples, however,are not exhaustive of the many possible embodiments of the disclosure.Without limiting the scope of the claims, some of the advantageousfeatures will now be summarized. Other objects, advantages and novelfeatures of the disclosure will be set forth in the following detaileddescription of the disclosure when considered in conjunction with thedrawings, which are intended to illustrate, not limit, the invention.

An aspect of the invention is directed to a system for reducingemissions in exhaust generated by an engine, said exhaust comprisingparticulates and volatile hydrocarbon condensables, the systemcomprising: a heat exchanger having an inlet that receives said exhaustat a first temperature and an outlet that outputs said exhaust at asecond temperature, the second temperature lower than the firsttemperature, wherein said heat exchanger causes at least some of saidvolatile hydrocarbon condensables to condense; and a gasolineparticulate filter (GPF) having an inlet in fluid communication with theoutlet of said heat exchanger to receive said exhaust at said secondtemperature, said GPF having an outlet to output said exhaust, said GPFtrapping at least some liquid-phase volatile hydrocarbon condensablesand at least some of said particulates, thereby reducing said emissionsfrom said engine.

In one or more embodiments, the first temperature is at least about 650°F. In one or more embodiments, the second temperature is about 350° F.to about 450° F. In one or more embodiments, said heat exchangerincludes a valve in fluid communication with a cooled exhaust path and abypass exhaust path, said exhaust in said cooled exhaust path beingcooled by said heat exchanger, said exhaust in said bypass exhaust pathbypassing said heat exchanger.

In one or more embodiments, the system further comprises a controller inelectrical communication with said valve to adjust a ratio of exhaustthat passes through said cooled exhaust path and said bypass exhaustpath. In one or more embodiments, said controller is in electricalcommunication with first and second thermocouples, said firstthermocouple disposed proximal to said inlet of said heat exchanger,said second thermocouple disposed in an exhaust conduit that extendsfrom said heat exchanger to said GPF. In one or more embodiments, saidcontroller is configured to regenerate said GPF by adjusting anoperating position of said valve such that all exhaust passes throughsaid bypass exhaust path.

In one or more embodiments, said controller is configured to regeneratesaid GPF on a periodic basis. In one or more embodiments, saidcontroller is configured to regenerate said GPF only when said engine isin an idling state or a coasting state. In one or more embodiments, saidcontroller determines whether said engine is in said idling state orsaid coasting state based on one of or a combination of (a) a rotationalspeed of said engine and (b) a fuel intake of said engine. In one ormore embodiments, said controller is configured to regenerate said GPFfor a predetermined time period. In one or more embodiments, saidcontroller is configured to stop regenerating said GPF during saidpredetermined time period when said engine is in a drive state.

In one or more embodiments, said particulates includes black carbonparticles and brown carbon particles, said brown carbon particlesincluding said liquid-phase volatile hydrocarbon condensables. In one ormore embodiments, said GPF includes a coating that traps said at leastsome of said liquid-phase volatile hydrocarbon condensables and said atleast some of said particulates. In one or more embodiments, said GPFincludes one or more catalytic elements that promote chemical reactionsthat remove at least some carbon monoxide and at least some unburnedhydrocarbons from said exhaust.

In one or more embodiments, the system further comprises an exhaustconduit that extends from said heat exchanger to said GPF, said exhaustconduit including an air inlet to receive a stream of injected air. Inone or more embodiments, the system further comprises an assemblycomprising said GPF and a second stage catalytic converter. In one ormore embodiments, said second stage catalytic converter includes one ormore catalytic elements that promote chemical reactions that remove atleast some carbon monoxide and at least some unburned hydrocarbons fromsaid exhaust.

In one or more embodiments, the system further comprises an exhaustconduit that extends from said heat exchanger to said GPF, said exhaustconduit including an air inlet to receive a stream of injected air. Inone or more embodiments, the system further comprises a first stagecatalytic converter disposed between said engine and said heatexchanger, said first stage catalytic converter including one or morecatalytic elements that promote chemical reactions that remove at leastsome NO_(x) compounds from said exhaust.

Another aspect of the invention is directed to a method of reducingemissions in exhaust generated by an engine, said exhaust comprisingparticulates and volatile hydrocarbon condensables, the methodcomprising: cooling said exhaust from a first temperature to a secondtemperature, said cooling causing a first portion of said volatilehydrocarbon condensables in said exhaust to condense into liquid-phasevolatile hydrocarbon condensables; passing said exhaust, including saidliquid-phase volatile hydrocarbon condensables and said particulates,through a gas particulate filter (GPF); and trapping, in said GPF, atleast some of said liquid-phase volatile hydrocarbon condensables and atleast some of said particulates.

In one or more embodiments, said first temperature is at least about650° F. In one or more embodiments, the second temperature is about 350°F. to about 450° F. In one or more embodiments, said cooling comprises:passing a first stream of said exhaust through a cooled exhaust path;passing a second stream of said exhaust through a bypass exhaust path;and combining said first and second streams of said exhaust to form acombined exhaust stream, said combined exhaust stream having said secondtemperature. In one or more embodiments, the method further comprisespassing said first stream of said exhaust through a heat exchanger. Inone or more embodiments, the method further comprises controlling aratio of exhaust in said first stream and said second stream to adjustsaid second temperature. In one or more embodiments, the method furthercomprises adjusting an operating position of a valve to control saidratio, said valve fluidly coupled to said first stream and said secondstreams.

In one or more embodiments, the method further comprises temporarilystopping said cooling to regenerate said GPF. In one or moreembodiments, the method further comprises regenerating said GPF on aperiodic basis. In one or more embodiments, the method further comprisesdetermining whether said engine is in an idling state or a coastingstate; and regenerating said GPF only when said engine is in said idlingstate or said coasting state. In one or more embodiments, said idlingstate and said coasting state is determined based on one of or acombination of (a) a rotational speed of said engine and (b) a fuelintake of said engine. In one or more embodiments, the method furthercomprises regenerating said GPF for a predetermined time period. In oneor more embodiments, the method further comprises stopping saidregenerating when said engine is in a drive state.

In one or more embodiments, at least some of said liquid-phase volatilehydrocarbon condensables are condensed on a first group of black carbonparticles to form brown carbon particles. In one or more embodiments,the method further comprises trapping at least some of a second group ofblack carbon particles and at least some of said brown carbon particlesin said GPF.

In one or more embodiments, the method further comprises passing saidcooled exhaust over one or more catalytic elements that promote chemicalreactions that remove at least some carbon monoxide and at least someunburned hydrocarbons from said exhaust. In one or more embodiments,said one or more catalytic elements are disposed in said GPF. In one ormore embodiments, said one or more catalytic elements are disposed in asecond stage catalytic converter, said second stage catalytic converterdisposed downstream of said GPF. In one or more embodiments, the methodfurther comprises injecting air into said cooled exhaust before passingsaid exhaust through said GPF, said air increasing an oxygen content ofsaid exhaust. In one or more embodiments, the method further comprises,prior to said cooling, passing said exhaust over one or more catalyticelements that promote chemical reactions that remove at least someNO_(x) compounds from said exhaust.

IN THE DRAWINGS

For a fuller understanding of the nature and advantages of the presentinvention, reference is made to the following detailed description ofpreferred embodiments and in connection with the accompanying drawings,in which:

FIG. 1 is a block diagram of an underbody of a vehicle according to theprior art;

FIG. 2 is a block diagram of an exhaust treatment system according toone or more embodiments of the invention;

FIG. 3 is a block diagram of an exhaust treatment system according toone or more embodiments of the invention;

FIG. 4 is a flow chart of a method for reducing particulate matter,hydrocarbons, nitrogen oxides, and carbon monoxide from exhausts ofinternal combustion engines;

FIG. 5 is a flow chart of a method for operating and regenerating aGPF/cGPF in an exhaust treatment system;

FIG. 6 is a block diagram of an exhaust treatment system for reducingemissions of volatile hydrocarbon condensables according to one or moreembodiments of the invention; and

FIG. 7 is a flow chart of a method for reducing volatile hydrocarboncondensables from exhausts of internal combustion engines.

DETAILED DESCRIPTION

Aspects of the invention are directed to reducing particulate andvolatile hydrocarbon emissions from the exhaust of an internalcombustion engine. The exhaust gas is cooled from a first temperature toa second temperature in an exhaust gas cooler (e.g., a heat exchanger)such that a first portion of the volatile hydrocarbon condensables inthe exhaust condense to the liquid phase and a second portion of thevolatile hydrocarbon condensables in the exhaust condense on blackcarbon particles to form semivolatile brown carbon particulates. Some orall of the liquid-phase volatile hydrocarbon condensables and thesemivolatile brown carbon particulates are trapped in a GPF or cGPFlocated downstream of the exhaust gas cooler.

FIG. 2 is a block diagram of an exhaust treatment system 20 according toone or more embodiments of the invention. The system 20 includes a firststage catalytic converter 210, an exhaust heat exchanger 220, an airpump 230, a second stage catalytic converter/cGPF 240, a muffler andtailpipe 250, and a controller 260. Exhaust from an internal combustionengine 200 enters the first stage catalytic converter 210 through aconduit, which can be connected to each cylinder of the engine 200 via amanifold. The exhaust enters the first stage catalytic converter 200 ator near the operating temperature of the engine. At steady state (i.e.,after the engine has warmed up from a cold start), engine 200 generallyoperates in the range of about 650° F. to about 1250° F. As used herein,“about” means plus or minus 10% of the relevant value. Engine 200 can bea spark-ignited internal combustion engine or a diesel engine. Inaddition, engine 200 can be in a vehicle or it can be stationary, forexample to drive a combined heat and power (CHP) system.

The engine 200 can operate with an air-fuel ratio (AFR) in the rich burnregime (i.e., less than or equal to a stoichiometric AFR). In someembodiments, the stoichiometric AFR is 14.64:1 (by mass) for gasoline.The stoichiometric AFR can vary depending on the type of fuel. Forexample, the stoichiometric AFR can be lower if the fuel includesethanol. As an example, E85 fuel (85% ethanol, 15% gasoline) can have astoichiometric AFR of about 9.8:1. When the engine 200 operates in therich burn regime, the exhaust contains a minimal or a substantially zerooxygen content. For example, the oxygen content can be less than orequal to about 0.1% by volume, less than or equal to about 0.05% byvolume, and/or less than or equal to about 0.025% by volume.

The first stage and second stage catalytic converters 210, 240 caninclude a catalyst comprising one or more platinum-group metals (PGMs),such as Pt, Pd, and/or Rh. In some embodiments, one or both of the firstand second stage catalytic converters 210, 240 include a TWC. The firststage catalytic converter 210 promotes chemical reactions (e.g.,reduction reactions) that remove at least some NO_(x) compounds from theexhaust stream (e.g., by reducing NO_(x) to form N₂ and O₂).

After passing through the first stage catalytic converter 210, theexhaust flows into the exhaust heat exchanger 220 (e.g., into an inletof heat exchanger 220) which lowers the temperature of the exhaust froma first temperature to a second temperature, the second temperaturelower than the first temperature. The first temperature can be at ornear the steady-state operating temperature of the engine 200 (e.g., atleast about 650° F. such as about 650° F. to about 1250° F.). The secondtemperature can be about 400° F., such about 350° F. to about 450° F.,including about 375° F., about 400° F., about 425° F., about 450° F., orany value or range between any two of the foregoing values. The heatexchanger 220 includes a cooled path in which heat exchanger 220 coolsthe exhaust and an optional bypass path that is not cooled by the heatexchanger 220. The cooled and optional bypass paths of the heatexchanger 220 converge at the downstream end of the heat exchanger 220,where the paths mix and have a temperature T_(mix). The exhaust thatflows through the cooled path can be cooled to a temperature of about250° F. to about 350° F., including about 275° F., about 300° F., about325° F., or any value or range between any two of the foregoing values.The heat exchanger 220 cools the exhaust with a cooling fluid, such asradiator fluid or coolant, which is in thermal communication with theexhaust that flows through the cooled path. For example, the coolingfluid can be received from the vehicle's radiator and pass through acoil that provides a surface area for thermal communication between thecooling fluid and the exhaust flowing through the cooled path.

The temperature T_(mix) can be adjusted by varying the flow rates (e.g.,volumetric and/or mass flow rates) or the ratio of flow rates (e.g.,volumetric and/or mass flow rates) of the exhaust in each path. Forexample, the heat exchanger 220 can include a bypass valve 270, in fluidcommunication (and/or fluidly coupled) with the cooled and bypass paths,that can be adjusted to vary the flow rate of the exhaust in the bypasspath. When the bypass valve 270 is fully closed, all of the exhaustflows through the cooled path. When the bypass valve 270 is fully open,the exhaust flows through both the cooled and bypass paths withoutrestriction. The bypass valve can also be partially opened or closed tolimit the flow rate of exhaust through the bypass path. In analternative embodiment, fully closing the bypass valve 270 causes all ofthe exhaust to flow through the cooled path, fully opening the bypassvalve 270 causes all of the exhaust to flow through the bypass path, andpartially opening the bypass valve 270 causes some exhaust to flowthrough the cooled and bypass paths, the respective amount/ratiodepending on the operating position of the bypass valve 270.

In some embodiments, the heat exchanger 220 can also include a cooledpath valve to open or close the cooled path. For example, during coldstart the cooled path valve can be fully closed while the bypass valve270 is fully open so the exhaust is at a maximum temperature when itpasses through the second stage catalytic converter 240 to promote thechemical reactions at the second stage catalytic converter 240.Alternatively, the heat exchanger 220 can include a valve at itsupstream side to direct the exhaust to either the cooled or bypass path,or to both the cooled and bypass paths. Any of the foregoing valves canbe adjusted by controller 260, which receives as inputs a firsttemperature of the exhaust before it enters the heat exchanger 220,measured by thermocouple 225 (e.g., located proximal to the inlet ofheat exchanger 220), and a second temperature of the exhaust after itexits the heat exchanger 220, measured by thermocouple 235 (e.g.,located in the exhaust conduit that extends from the outlet of heatexchanger 220 to the inlet of second stage catalytic converter/cGPF240). The controller 260 adjusts the valve(s) (e.g., valve 270) so thatthe second temperature is at a set point temperature of about 400° F.,such as about 350° F. to about 450° F., as discussed above.

When the exhaust gas is cooled by the heat exchanger 220 to about 400°F., at least some or most of the gaseous condensables (e.g., volatileunburned hydrocarbons) undergo a phase change and condense as a liquid.Thus, the reduction in temperature of the exhaust stream causes a higherfraction of the condensables to reach their liquid phase while stillcontained in the exhaust gas stream. The reduction in temperature hasthe added benefit of forming more brown carbon when some of the gaseouscondensables condense on the black carbon particles that act asnucleation sites during the phase change process.

After the exhaust gas exits the heat exchanger 220, it passes through aconduit that receives a volume of air injected by air pump 230. Theinjected air increases the oxygen concentration of the exhaust before itpasses through the second stage catalytic converter 240. The increasedoxygen concentration promotes oxidation reactions in the second stagecatalytic converter that remove carbon monoxide and unburnedhydrocarbons from the exhaust. The air pump 230 can inject unheated airtaken from outside of the vehicle, which can have a temperature in therange of about 32° F. (or lower in the winter) to about 90° F. (orhigher in the summer), depending on the climate in which the vehicle islocated. The unheated air can cause the temperature of the exhaust todecrease. In other embodiments, the injected air is preheated in whichcase it has little effect on the exhaust temperature. To control for thetemperature change caused by the injected air, thermocouple 235 ispreferably located downstream of the injected air inlet to provide theappropriate feedback temperature to controller 260. Likewise, theinjected air inlet is preferably located upstream of thermocouple 235and downstream of heat exchanger 220. In some embodiments, the air pump230 is also in electrical communication with the controller 260, forexample to adjust the oxygen concentration based on feedback from anoxygen sensor disposed downstream of the injected air inlet.

After receiving the injected air from air pump 230, the exhaust passesinto the second stage catalytic converter 240. As discussed above, thesecond stage catalytic converter 240 promotes chemical reactions (e.g.,oxidation reactions) that remove at least some carbon monoxide and atleast some unburned hydrocarbons from the exhaust stream. At the reducedtemperature that the exhaust enters the second stage catalytic converter240 (i.e., about 400° F., such as about 350° F. to about 450° F.), theoxidation reactions occur without reforming nitrogen oxide compounds,which are controlled by emissions regulators. In some embodiment, thesecond stage catalytic converter 240 can also reduce the concentrationof any remaining NO_(x) in the exhaust.

The second stage catalytic converter 240 also includes a GPF. The GPFcan be a separate unit (e.g., a modular portion of an assembly thatincludes a second stage catalytic converter) of the second stagecatalytic converter 240 or it can be integrated into the second stagecatalytic converter 240. In some embodiments, the second stage catalyticconverter is a cGPF, which can include some or all catalytic elementsthat are also disposed in the second stage catalytic converter 240. Forexample, the cGPF can include one or more of the above-describedplatinum-group metals and/or it can include the catalysts that aretypically included in a TWC. In some embodiments, the second stagecatalytic converter 240 and/or cGPF is integrated into a single unitthat also includes the muffler 250. In an alternative embodiment, a GPFis disposed between the second stage catalytic converter 240 and theinjected air inlet for air pump 230.

The GPF or cGPF (in general, GPF) includes a coating 245 that trapsparticulate emissions, such as black and brown carbon, in the exhaust.The coating 245 can be a coating as known in the art. A three-waycatalyst washcoat containing one or more PGMs and/or other metals withoxygen-storage capability may be added or included in coating 245. Thecoating 245 also collects the additional brown carbon and theliquid-phase condensables formed as a result of the lower exhausttemperature. Therefore, the reduction in temperature allows the GPF totrap more volatile hydrocarbon condensables, as liquid and as browncarbon, than it could when the exhaust is at a higher temperature (e.g.,higher than about 400° F.) where the liquid phase change does not occur.This reduction in the concentration of hydrocarbon condensables reducesthe overall hydrocarbon emissions and reduces the chance of condensablesforming particulates as the exhaust exits the tailpipe.

Aspects of the invention described herein can provide one or more of thefollowing advantages:

(1) Cooling the exhaust gases in an exhaust gas cooler (e.g., heatexchanger 220) after the first stage catalytic converter (e.g., firststage catalytic converter 210) condenses a larger fraction of gaseoushydrocarbons into their liquid phase while they are still in the exhaustsystem (e.g., exhaust treatment system 20). These can be captured by theGPF/cGPF, making it more effective in removing a larger fraction of thecondensables in liquid form and as solid particulates (e.g., browncarbon) that carry the liquefied condensables.

(2) Cooling the exhaust gases in an exhaust gas cooler (e.g., heatexchanger 220) after the first stage catalytic converter (e.g., firststage catalytic converter 210) results in the formation of particlescontaining large fractions of semivolatiles (e.g., brown carbon) thatcan be more easily captured in the GPF due to their larger size. Becausea higher fraction of the particles forming after the exhaust gas coolerhas larger sizes, it helps the GPF filtration system to remove moreparticulate mass and particulate numbers leaving the exhaust stream(e.g., exhaust treatment system 20) with a much smaller fraction ofcondensable hydrocarbons.

(3) Employing a catalyzed GPF (cGPF) can have the added benefit ofreducing/replacing the second stage catalytic converter. Thus, theexhaust system (e.g., exhaust treatment system 20) can haveapproximately the same footprint and take up approximately the sameamount of space as existing exhaust systems.

(4) Employing other forms of exhaust gas cooling systems (i.e.,different than heat exchanger 220) that cool down the entire exhauststream or fractions of it before treatment in the GPF/cGPF is alsopossible and will lead to similar benefits

(5) The systems and processes described herein can be used in internalcombustion engine designs that utilize exhaust gas recirculation toreduce NO formation in the engine and/or to improve the engineefficiency.

(5) In a standard emissions system without intermediate exhaust cooling,the GPF/cGPF is regenerated by temporarily running the engine's AFRunder fuel lean conditions to provide extra oxygen at the hightemperatures necessary to oxidize the particulate matter caught in thefilter. This may greatly increase the formation and/or reformation ofnitrogen oxides, for example in the second catalytic converter. Becausethe above system 20 includes additional air for oxidation (i.e., airinjected by air pump 230), regeneration of the GPF can be accomplishedby temporarily increasing the temperature at the second stage catalyticconverter 240 (e.g., by closing the cooled path valve) without changingthe engine's AFR. While this may induce a slight increase in nitrogenoxides due to reformation, the overall tailpipe levels are much lowerthan would be produced by leaning the AFR. Nitrogen oxide reformationcan be further reduced by increasing the temperature at a time whenminimal fuel is consumed by the engine, such as when coasting down ahill or idling. Such regeneration can occur on a periodic basis, forexample once a day, once a week, once every 1,000 miles, or otherinterval or periodic basis.

FIG. 3 is a block diagram of an exhaust treatment system 30 according toone or more embodiments of the invention. System 30 is the same orsimilar to system 20 except as described below. In place of the combinedsecond stage catalytic converter/cGPF 240 in system 20, system 30includes a GPF 380 disposed between the inlet for the air injected byair pump 230 and the inlet to second stage catalytic converter 340. Inan alternative embodiment, the GPF 380 can be disposed between theoutlet of heat exchanger 220 and the inlet for the air injected by airpump 230. The second stage catalytic converter 340 is otherwise the sameor similar to second stage catalytic converter 240. For example, secondstage catalytic converter 340 can include one or more platinum-groupmetals and/or it can include a TWC in some embodiments.

GPF 380 is the same or similar to the GPF described above with respectto second stage catalytic converter/cGPF 240. For example, GPF 380includes a coating 345 which is the same or similar to coating 245.Thus, coating 345 can trap black carbon, brown carbon, and condensablesin liquid form. It is noted that if additional GPFs are desired insystem 30, the second stage catalytic converter 340 can include a secondGPF or, alternatively, it can include or can be a cGPF, as describedabove.

In an alternative embodiment, the air pump 230 and/or the second stagecatalytic converter 340 are not included in system 30. When the air pump230 and/or second stage catalytic converter 340 are removed from system30, the GPF 345 still functions to trap black carbon, brown carbon, andcondensables in liquid form, as discussed above.

FIG. 4 is a flow chart 40 of a method for reducing particulate matter,hydrocarbons, nitrogen oxides, and carbon monoxide from exhausts ofinternal combustion engines. The method according to flow chart 40 canbe performed on system 20 and/or 30, described above. In step 400, theexhaust is passed through a first stage catalytic converter. The firststage catalytic converter includes one or more active catalytic elements(e.g., a platinum-group metal and/or a TWC) that catalyzes a chemicalreaction to reduce the concentration of nitrogen oxide compounds in theexhaust. The exhaust is generated by an internal combustion engine whichcan run at a stoichiometric or a rich AFR, as described above. In step410, the exhaust is cooled to about 400° F., such as about 350° F. toabout 450° F. The exhaust can be cooled by passing some or all of itthrough a heat exchanger or by using another cooling unit. As discussedabove, a portion of the exhaust can bypass the cooling unit and the flowrate and/or ratio of cooled and bypassed exhaust can be controlled(e.g., by valves in communication with a controller) to provide thedesired temperature.

In step 420, the lower temperature causes at least a portion or most ofthe volatile hydrocarbon condensables to undergo a phase change into aliquid. The liquid-phase condensables can remain as liquid and/or theycan condense on the black carbon particles, that act as nucleation sitesduring the phase change process, to form semivolatile brown carbon, asdiscussed above. In step 430, the oxygen concentration of the cooledexhaust is increased to at least about 0.25%, such as at least about0.5%, at least about 0.75%, at least about 1%, or a higherconcentration. The oxygen concentration can be increased by injectingair into the cooled exhaust stream. In step 440, the exhaust is passedthrough a GPF that includes a coating to trap the liquid-phasecondensables and semivolatile particles formed in step 420 in additionto other particulates in the exhaust such as black carbon. In step 440,the exhaust is passed through a second stage catalytic converter. Thesecond stage catalytic converter includes one or more active catalyticelements (e.g., a platinum-group metal and/or a TWC) that catalyzeschemical reactions to reduce the concentration of unburned hydrocarbonsand carbon monoxide in the exhaust. The second stage catalytic convertercan also reduce the concentration of nitrogen oxide compounds in someembodiments.

FIG. 5 is a flow chart 50 of a method for operating and regenerating aGPF/cGPF (in general, GPF) in an exhaust treatment system. The methodaccording to flow chart 50 can be performed on system 20 and/or 30,described above. In step 500, the GPF collects or traps particulates,such as black and brown carbon, and liquid-phase condensables from theexhaust stream. After a first predetermined period or interval (e.g.,once a day or every 100 miles), a controller in the exhaust treatmentsystem at step 510 determines whether the regeneration period for theGPF has been exceeded. The regeneration period can be based on time(e.g., once a day, once a week, once a month, or other time period),based on mileage (e.g., every 500 miles, every 1,000 miles, or othermileage interval), based on a combination of time or mileage (e.g., oncea week or once every 300 miles, whichever occurs first), or otherfactors. The regeneration period can occur on a periodic or anon-periodic basis. If the controller determines that the regenerationperiod has not been exceeded, the flow chart returns to step 500 and theGPF continues to collect particulates (e.g., black and/or brown carbonparticulates) and liquid-phase condensables from the exhaust. If thecontroller determines that the regeneration period has been exceeded,the controller then determines at step 520 whether the engine is in anidling or coasting state (and/or that the engine is not in a drivestate), for example based on the engine's rotational speed (e.g., RPMs)and/or the fuel intake of the engine. If the engine is not in an idlingor coasting state (and/or if the engine is in a drive state), the flowchart 50 returns to step 500 and the GPF continues to collectparticulates and liquid-phase condensables from the exhaust for a secondpredetermined period, or interval which can be the same or less than thefirst predetermined period or interval. For example, the secondpredetermined period can be less than an hour, such as 15 minutes, orless than 10 miles in some embodiments.

After the controller determines at step 520 that the engine is in anidling or coasting state (and/or not in a drive state), the controllerat step 530 causes the temperature of the exhaust exiting the coolingunit to increase (e.g., by adjusting the bypass valve and/or coolingvalve). The temperature of the exhaust exiting the cooling unit canraised to about 500° F. to about 1,000° F., such as about 600° F., about700° F., about 800° F., about 900° F., or any value or range between anytwo of the foregoing values. In step 540, the GPF regenerates using thehigh temperature exhaust.

On a periodic basis or interval, the controller checks whether theregeneration is complete in step 550, which can be based on apredetermined time period. If the regeneration is complete, the flowchart 50 proceeds to step 570 where the controller causes the coolingunit to lower the temperature of the exhaust exiting the cooling unit toan operating temperature of about 400° F., as discussed above. After theexhaust temperature is decreased in step 570, the flow chart 50 returnsto step 500 where the GPF collects particulates and liquid-phasecondensables from the exhaust. The controller also resets the firstpredetermined time period and the regeneration period.

If the regeneration is not complete in step 550, the flow chart proceedsto step 560 where the controller determines whether the engine continuesto be in an idling or coasting state (and/or that the engine is not in adrive state). If the engine is in an idling or coasting state, the flowchart 50 returns to step 540 to continue to regenerate the GPF using thehigh temperature exhaust. If the engine is not in an idling or coastingstate (and/or if the engine is in a drive state), the flow chart 50proceeds to step 570 to decrease the exhaust temperature, as discussedabove. After the exhaust temperature is decreased in step 570, the flowchart 50 returns to step 500 where the GPF collects particulates andliquid-phase condensables from the exhaust. The controller can reset thefirst predetermined period and/or the regeneration period to asecondary, lower period so that the controller attempts to complete theregeneration sooner than it normally would. Alternatively, thecontroller can set the first predetermined period and/or theregeneration period to zero, in which case flow chart 50 passesimmediately to steps 510 and 520 in an attempt to complete the GPFregeneration process.

FIG. 6 is a block diagram of an exhaust treatment system 60 for reducingemissions of volatile hydrocarbon condensables according to one or moreembodiments of the invention. Exhaust treatment system 60 includes anexhaust heat exchanger 620, a controller 660, and a GPF 680. Heatexchanger 620, controller 670, and GPF 680 can be the same as orsubstantially the same as heat exchanger 220, controller 260, and GPF380, respectively. Accordingly, exhaust treatment system 60 operates inthe same or substantially the same way as exhaust treatment system 30with respect to heat exchanger 220, controller 260, and GPF 380.

In operation, exhaust from an engine passes through an exhaust conduitand into an inlet of heat exchanger 620 at a temperature at or near theoperating temperature of the engine (e.g., about 650° F. to about 1250°F.). Upstream of the heat exchanger 620, the exhaust can optionally passthrough a first stage catalytic converter, as discussed above. Thecontroller 660 adjusts the operating position of one or more valves(e.g., bypass valve 670) in the heat exchanger 620, based on feedbackfrom thermocouples 625, 635) to adjust the flow rate and/or ratio ofexhaust that passes through a cooled path and a bypass path such thatthe temperature of the exhaust exiting the heat exchanger 620 is about400° F. (e.g., about 350° F. to about 450° F.), as discussed above. Thereduction in temperature causes a portion or most of the volatilehydrocarbon condensables in the exhaust to undergo a phase change into aliquid, which are trapped or collected by GPF 680 as liquid and as browncarbon, as discussed above. GPF 680 can also collect black carbonparticles in the exhaust.

In some embodiments, GPF 680 can be a cGPF as discussed above. Inaddition or in the alternative, a second stage catalytic converter canbe disposed downstream of the GPF 680, as discussed above.

FIG. 7 is a flow chart 70 of a method for reducing volatile hydrocarboncondensables from exhausts of internal combustion engines. The methodaccording to flow chart 40 can be performed on system 20, 30, and/or 40,described above. Steps 700, 710, and 720 can be the same as orsubstantially the same as steps 410, 420, and 440, respectively. It isnoted that in step 720 the exhaust can pass through either a GPF or acGPF. In step 730, the liquid-phase condensables and particulates (e.g.,black carbon and/or semivolatile brown carbon particles) are trapped inthe GPF/cGPF.

In the foregoing specification, the invention has been described withreference to specific embodiments. However, one of ordinary skill in theart appreciates that various modifications and changes can be madewithout departing from the scope of the disclosure and technologydescribed herein. Accordingly, the specification and figures are to beregarded in an illustrative rather than a restrictive sense, and allsuch modifications are intended to be included within the scope of theclaims and this disclosure.

What is claimed is:
 1. A method of reducing emissions in exhaustgenerated by an engine, said exhaust comprising particulates andvolatile hydrocarbon condensables, the method comprising: cooling saidexhaust from a first temperature to a second temperature, said coolingcausing a first portion of said volatile hydrocarbon condensables insaid exhaust to condense into liquid-phase volatile hydrocarboncondensables; passing said exhaust, including said liquid-phase volatilehydrocarbon condensables and said particulates, through a gasparticulate filter (GPF); and trapping, in said GPF, at least some ofsaid liquid-phase volatile hydrocarbon condensables and at least some ofsaid particulates.
 2. The method of claim 1, wherein said firsttemperature is at least about 650° F.
 3. The method of claim 1, whereinthe second temperature is about 350° F. to about 450° F.
 4. The methodof claim 1, wherein said cooling comprises: passing a first stream ofsaid exhaust through a cooled exhaust path; passing a second stream ofsaid exhaust through a bypass exhaust path; and combining said first andsecond streams of said exhaust to form a combined exhaust stream, saidcombined exhaust stream having said second temperature.
 5. The method ofclaim 4, further comprising passing said first stream of said exhaustthrough a heat exchanger.
 6. The method of claim 4, further comprisingcontrolling a ratio of exhaust in said first stream and said secondstream to adjust said second temperature.
 7. The method of claim 6,further comprising adjusting an operating position of a valve to controlsaid ratio, said valve fluidly coupled to said first stream and saidsecond streams.
 8. The method of claim 1, further comprising temporarilystopping said cooling to regenerate said GPF.
 9. The method of claim 8,further comprising regenerating said GPF on a periodic basis.
 10. Themethod of claim 8, further comprising: determining whether said engineis in an idling state or a coasting state; and regenerating said GPFonly when said engine is in said idling state or said coasting state.11. The method of claim 10, wherein said idling state and said coastingstate is determined based on one of or a combination of (a) a rotationalspeed of said engine and (b) a fuel intake of said engine.
 12. Themethod of claim 10, further comprising regenerating said GPF for apredetermined time period.
 13. The method of claim 12, furthercomprising stopping said regenerating when said engine is in a drivestate.
 14. The method of claim 1, wherein at least some of saidliquid-phase volatile hydrocarbon condensables are condensed on a firstgroup of black carbon particles to form brown carbon particles.
 15. Themethod of claim 14, further comprising trapping at least some of asecond group of black carbon particles and at least some of said browncarbon particles in said GPF.
 16. The method of claim 1, furthercomprising passing said cooled exhaust over one or more catalyticelements that promote chemical reactions that remove at least somecarbon monoxide and at least some unburned hydrocarbons from saidexhaust.
 17. The method of claim 16, wherein said one or more catalyticelements are disposed in said GPF.
 18. The method of claim 16, whereinsaid one or more catalytic elements are disposed in a second stagecatalytic converter, said second stage catalytic converter disposeddownstream of said GPF.
 19. The method of claim 16, further comprisinginjecting air into said cooled exhaust before passing said exhaustthrough said GPF, said air increasing an oxygen content of said exhaust.20. The method of claim 1, further comprising, prior to said cooling,passing said exhaust over one or more catalytic elements that promotechemical reactions that remove at least some NO_(x) compounds from saidexhaust.